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Snellen chart. Purpose. Snellen chart is used to estimate visual acuity (last three rows are 20/15, 20/13 and 20/10) A Snellen chart is an eye chart that can be used to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862 as a measurement tool for the acuity formula ...
For 6/6 = 1.0 acuity, the size of a letter on the Snellen chart or Landolt C chart is a visual angle of 5 arc minutes (1 arc min = 1/60 of a degree), which is a 43 point font at 20 feet. [10] By the design of a typical optotype (like a Snellen E or a Landolt C), the critical gap that needs to be resolved is 1/5 this value, i.e., 1 arc min.
The recent formula used by the Brannock device assumes a foot length of 2 barleycorns less than the length of the last; thus, men's size 1 is equivalent to a last's length of 8 + 1 ⁄ 3 in (21.17 cm) and foot's length of 7 + 2 ⁄ 3 in (19.47 cm), and children's size 1 is equivalent to 4 + 1 ⁄ 4 in (10.8 cm) last's length and 3 + 7 ⁄ 12 in ...
The rod, perch, or pole (sometimes also lug) is a surveyor's tool [1] and unit of length of various historical definitions. In British imperial and US customary units, it is defined as 16 + 1 ⁄ 2 feet, equal to exactly 1 ⁄ 320 of a mile, or 5 + 1 ⁄ 2 yards (a quarter of a surveyor's chain), and is exactly 5.0292 meters.
Shaku (Japanese: 尺) or Japanese foot[1][2] is a Japanese unit of length derived (but varying) from the Chinese chi, originally based upon the distance measured by a human hand from the tip of the thumb to the tip of the forefinger [3][a] (compare span). Traditionally, the length varied by location or use, but it is now standardized as 10/33 m ...
Miners also use it as a unit of area equal to 6 feet square (3.34 m 2) in the plane of a vein. [2] In Britain, it can mean the quantity of wood in a pile of any length measuring 6 feet (1.8 m) square in cross section. [2] In Central Europe, the klafter was the corresponding unit of comparable length, as was the toise in France.
Thus thousands of men under this height were denied the opportunity to fight in the war. As a result of pressure to allow them entry, special "Bantam Battalions" were created composed of men who were 4 feet 10 inches (147 cm) to 5 feet 3 inches (160 cm). By the end of the war there were 29 Bantam Battalions of about 1,000 men each.
From the time of Magellan's expeditions until the end of the 18th century, European explorers reported about the Patagonians 2.7 and 3.0 m (9 and 10 ft) tall, and even an individual about 4 or 4.5 m (13 or 15 ft) tall captured by Magellan's crewmen near the Santa Cruz River (Argentina). [179]